Additional outlets must often be added to underground pipelines or pipes. This is typically accomplished by creating an excavation from the earth's surface down to the pipe to be tapped. In locations where disturbance of the surface is not an issue an excavation is made which exposes the underground pipe and is large enough to accommodate a fitting along with a welder and his equipment. The fitting is temporarily held in place by various means while the welder physically and sealably secures the fitting by welding it to the exterior of the pipe. Once the fitting has been welded in place the means by which the fitting is temporarily held in place are removed. At this point an operation called a hot tap is carried out wherein a portion of the pipe is cut and removed such that the fitting is now in fluid communication with the interior of the pipe. This is accomplished while the pipe is under pressure carrying gas or liquids.
In many situations, such as pipes located under busy city streets, the surface disturbance caused by an excavation large enough to accommodate the fitting and welder are unacceptable. In these types of situations a much smaller excavation is created extending from the earth's surface down to just below the underground pipe being tapped. The excavation is deep enough to expose the lower surface of the pipe. The diameter of the excavation is typically just large enough to accommodate the fittings to be mounted on the pipe. A first portion of the fitting is seated on the lower surface of the pipe. The second portion of the fitting is then placed on a top portion of the pipe. The first and second portions are aligned with one another and secured to one another and the pipe using bolts. These bolt-on fittings are sealed to the pipe by elastomeric seals captured between the fitting and pipe. While these bolt-on fittings allow an underground pipe to be tapped with minimal disturbance to the surface, the elastomeric seals tend to deteriorate over time leading to leaks between the pipe and the fitting.
There is a long felt need in the pipeline industry for a fitting and method which would provide a permanent welded seal for a branch outlet while accessing the existing pipe using a keyhole excavation.
For additional information relating to excavation and fittings for tapping underground pipes, reference may be had to the following previously issued United States patents.
U.S. Pat. No.InventorTitle  847,594McCrearyHose or Pipe Mender3,178,793RosengartenApparatus For Sealing MainsJr. et al.4,323,526Hilbush IIIMethod For Sealing Pipe Joints4,610,439BurghardtService Saddle U-Bolt Installation Holder4,647,073KosakaClamping Device For Underground Pipes4,832,069Gale et al.Tapping Subterranean Pipes5,659,935Lo-PintoApparatus For Installing A Branchet al.Tapping On A Pipe6,142,165Wartel et al.Method and Apparatus For InstallingA Branch Connector FromThe Top Of An Excavation6,669,406Hutton et al.Method and Apparatus For UndergroundConnection of Pipe6,705,801Kiest Jr.Apparatus and Method For ProvidingAccess To Buried Pipeline7,001,106BurnhamInstallation of Service Connectionset al.For Sensors or Transmitters InBuried Water Pipes2006/0002765Hutton et al.Tool Assembly With Universal CouplingFor Various Tools, ForWork On Underground Pipes